ErrorZilla

A new (or new to me) Firefox extension that makes error pages much more handy.

Rather than the lone “Try again” button, ErrorZilla adds buttons to the error page that allow you to do things like view the Google Cache of the page, find a snapshot of the page from the Wayback Machine, ping the site, or see who owns the site with a WhoIs lookup (assuming, of course, any of this information exists for the site).